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                                <blockquote><p>&#x6700;&#x5F00;&#x59CB;<code>React.Children</code>&#x8FD9;&#x4E2A; API &#x662F;&#x4E0D;&#x60F3;&#x8BB2;&#x7684;&#xFF0C;&#x4E00;&#x65B9;&#x9762;&#x5E73;&#x65F6;&#x4E0D;&#x600E;&#x4E48;&#x7528;&#xFF0C;&#x53E6;&#x4E00;&#x65B9;&#x9762;&#x8DDF;&#x6570;&#x7EC4;&#x5904;&#x7406;&#x529F;&#x80FD;&#x5DEE;&#x4E0D;&#x591A;&#xFF0C;&#x4E0D;&#x6DF1;&#x7A76;&#x5B9E;&#x73B0;&#x662F;&#x6BD4;&#x8F83;&#x5BB9;&#x6613;&#x7406;&#x89E3;&#x7684;&#x3002;&#x4F46;&#x662F;&#x540E;&#x6765;&#x5B9E;&#x9645;&#x53BB;&#x770B;&#x4E86;&#x4E00;&#x4E0B;&#x6E90;&#x7801;&#x4E4B;&#x540E;&#x53D1;&#x73B0;&#xFF0C;&#x4ED6;&#x7684;&#x5B9E;&#x73B0;&#x65B9;&#x5F0F;&#x8FD8;&#x662F;&#x975E;&#x5E38;&#x6709;&#x8DA3;&#x7684;&#xFF0C;&#x5C24;&#x5176;&#x662F;<code>map</code>&#x548C;<code>forEach</code>&#xFF0C;&#x6211;&#x4EEC;&#x5C31;&#x6309;&#x7167;<code>map</code>&#x7684;&#x6D41;&#x7A0B;&#x6765;&#x770B;&#x4E00;&#x4E0B;&#xFF0C;<code>forEach</code>&#x5176;&#x5B9E;&#x5DEE;&#x4E0D;&#x591A;&#xFF0C;&#x53EA;&#x662F;&#x6CA1;&#x6709;&#x8FD4;&#x56DE;&#x65B0;&#x7684;&#x8282;&#x70B9;&#x3002;</p></blockquote><p>&#x5148;&#x6765;&#x770B;&#x4E00;&#x4E0B;&#x6D41;&#x7A0B;&#x56FE;&#xFF1A;</p><p><img alt="map&#x6D41;&#x7A0B;" src="https://pozvqg.dm.files.1drv.com/y4mmeXuR-FkgNj-8c2xEInueibhFoYSEdG7un9nWggJFV1nYGsjb6S8m0D776nWAyuXHwKz1kCVMelh96STs4RYe9EVppRjlQyiu7jwrPqH9iM-cR4YPS7UbJkFTZHg62yMg6k8n_c-DMQOoEzZhvmCdR8LAEPFY4JQvypWYj3LF1EpeR5zp6OIfkPOk3qei4Qwz903Q9lxtWpavsva6TceyQ?width=768&amp;height=1152&amp;cropmode=none"></p><p>&#x5F53;&#x7136;&#x8FD9;&#x4E48;&#x770B;&#x80AF;&#x5B9A;&#x4E91;&#x91CC;&#x96FE;&#x91CC;&#xFF0C;&#x63A5;&#x4E0B;&#x53BB;&#x4F1A;&#x5BF9;&#x5404;&#x4E2A;&#x51FD;&#x6570;&#x8FDB;&#x884C;&#x8BB2;&#x89E3;&#xFF0C;&#x7136;&#x540E;&#x518D;&#x56DE;&#x8FC7;&#x5934;&#x6765;&#x914D;&#x5408;&#x56FE;&#x7247;&#x89C2;&#x770B;&#x66F4;&#x597D;&#x7406;&#x89E3;&#x3002;</p><h3 id="&#x5F00;&#x59CB;">&#x5F00;&#x59CB;</h3><pre><code class="lang-js"><span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">mapChildren</span>(<span class="hljs-params">children, func, context</span>) </span>{
  <span class="hljs-keyword">if</span> (children == <span class="hljs-literal">null</span>) {
    <span class="hljs-keyword">return</span> children
  }
  <span class="hljs-keyword">const</span> result = []
  mapIntoWithKeyPrefixInternal(children, result, <span class="hljs-literal">null</span>, func, context)
  <span class="hljs-keyword">return</span> result
}

<span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">mapIntoWithKeyPrefixInternal</span>(<span class="hljs-params">children, array, prefix, func, context</span>) </span>{
  <span class="hljs-keyword">let</span> escapedPrefix = <span class="hljs-string">&apos;&apos;</span>
  <span class="hljs-keyword">if</span> (prefix != <span class="hljs-literal">null</span>) {
    escapedPrefix = escapeUserProvidedKey(prefix) + <span class="hljs-string">&apos;/&apos;</span>
  }
  <span class="hljs-keyword">const</span> traverseContext = getPooledTraverseContext(
    array,
    escapedPrefix,
    func,
    context,
  )
  traverseAllChildren(children, mapSingleChildIntoContext, traverseContext)
  releaseTraverseContext(traverseContext)
}</code></pre>
<p><code>map</code>&#x548C;<code>forEach</code>&#x7684;&#x6700;&#x5927;&#x533A;&#x522B;&#x5C31;&#x662F;&#x6709;&#x6CA1;&#x6709;<code>return result</code>&#x3002;</p><p><code>getPooledTraverseContext</code>&#x5C31;&#x662F;&#x4ECE;<code>pool</code>&#x91CC;&#x9762;&#x627E;&#x4E00;&#x4E2A;&#x5BF9;&#x8C61;&#xFF0C;<code>releaseTraverseContext</code>&#x4F1A;&#x628A;&#x5F53;&#x524D;&#x7684;<code>context</code>&#x5BF9;&#x8C61;&#x6E05;&#x7A7A;&#x7136;&#x540E;&#x653E;&#x56DE;&#x5230;<code>pool</code>&#x4E2D;&#x3002;</p><pre><code class="lang-js"><span class="hljs-keyword">const</span> POOL_SIZE = <span class="hljs-number">10</span>
<span class="hljs-keyword">const</span> traverseContextPool = []
<span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">getPooledTraverseContext</span>(<span class="hljs-params"></span>) </span>{
  <span class="hljs-comment">// args</span>
  <span class="hljs-keyword">if</span> (traverseContextPool.length) {
    <span class="hljs-keyword">const</span> traverseContext = traverseContextPool.pop()
    <span class="hljs-comment">// set attrs</span>
    <span class="hljs-keyword">return</span> traverseContext
  } <span class="hljs-keyword">else</span> {
    <span class="hljs-keyword">return</span> {
      <span class="hljs-comment">/* attrs */</span>
    }
  }
}

<span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">releaseTraverseContext</span>(<span class="hljs-params">traverseContext</span>) </span>{
  <span class="hljs-comment">// clear attrs</span>
  <span class="hljs-keyword">if</span> (traverseContextPool.length &lt; POOL_SIZE) {
    traverseContextPool.push(traverseContext)
  }
}</code></pre>
<p>&#x90A3;&#x4E48;&#x6309;&#x7167;&#x8FD9;&#x4E2A;&#x6D41;&#x7A0B;&#x6765;&#x770B;&#xFF0C;&#x662F;&#x4E0D;&#x662F;<code>pool</code>&#x6C38;&#x8FDC;&#x90FD;&#x53EA;&#x6709;&#x4E00;&#x4E2A;&#x503C;&#x5462;&#xFF0C;&#x6BD5;&#x7ADF;&#x63A8;&#x51FA;&#x4E4B;&#x540E;&#x64CD;&#x4F5C;&#x5B8C;&#x4E86;&#x5C31;&#x63A8;&#x5165;&#x4E86;&#xFF0C;&#x8FD9;&#x4E48;&#x5FAA;&#x73AF;&#x7740;&#x3002;&#x7B54;&#x6848;&#x80AF;&#x5B9A;&#x662F;&#x5426;&#x7684;&#xFF0C;&#x8FD9;&#x5C31;&#x8981;&#x8BB2;&#x5230;<code>React.Children.map</code>&#x7684;&#x4E00;&#x4E2A;&#x7279;&#x6027;&#x4E86;&#xFF0C;&#x90A3;&#x5C31;&#x662F;&#x5BF9;&#x6BCF;&#x4E2A;&#x8282;&#x70B9;&#x7684;<code>map</code>&#x8FD4;&#x56DE;&#x7684;&#x5982;&#x679C;&#x662F;&#x6570;&#x7EC4;&#xFF0C;&#x90A3;&#x4E48;&#x8FD8;&#x4F1A;&#x7EE7;&#x7EED;&#x5C55;&#x5F00;&#xFF0C;&#x8FD9;&#x662F;&#x4E00;&#x4E2A;&#x9012;&#x5F52;&#x7684;&#x8FC7;&#x7A0B;&#x3002;&#x63A5;&#x4E0B;&#x53BB;&#x6211;&#x4EEC;&#x5C31;&#x6765;&#x770B;&#x770B;&#x3002;</p><pre><code class="lang-js"><span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">traverseAllChildren</span>(<span class="hljs-params">children, callback, traverseContext</span>) </span>{
  <span class="hljs-keyword">if</span> (children == <span class="hljs-literal">null</span>) {
    <span class="hljs-keyword">return</span> <span class="hljs-number">0</span>
  }

  <span class="hljs-keyword">return</span> traverseAllChildrenImpl(children, <span class="hljs-string">&apos;&apos;</span>, callback, traverseContext)
}

<span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">traverseAllChildrenImpl</span>(<span class="hljs-params">
  children,
  nameSoFar,
  callback,
  traverseContext,
</span>) </span>{
  <span class="hljs-keyword">const</span> type = <span class="hljs-keyword">typeof</span> children

  <span class="hljs-keyword">if</span> (type === <span class="hljs-string">&apos;undefined&apos;</span> || type === <span class="hljs-string">&apos;boolean&apos;</span>) {
    children = <span class="hljs-literal">null</span>
  }

  <span class="hljs-keyword">let</span> invokeCallback = <span class="hljs-literal">false</span>

  <span class="hljs-keyword">if</span> (children === <span class="hljs-literal">null</span>) {
    invokeCallback = <span class="hljs-literal">true</span>
  } <span class="hljs-keyword">else</span> {
    <span class="hljs-keyword">switch</span> (type) {
      <span class="hljs-keyword">case</span> <span class="hljs-string">&apos;string&apos;</span>:
      <span class="hljs-keyword">case</span> <span class="hljs-string">&apos;number&apos;</span>:
        invokeCallback = <span class="hljs-literal">true</span>
        <span class="hljs-keyword">break</span>
      <span class="hljs-keyword">case</span> <span class="hljs-string">&apos;object&apos;</span>:
        <span class="hljs-keyword">switch</span> (children.$$<span class="hljs-keyword">typeof</span>) {
          <span class="hljs-keyword">case</span> REACT_ELEMENT_TYPE:
          <span class="hljs-keyword">case</span> REACT_PORTAL_TYPE:
            invokeCallback = <span class="hljs-literal">true</span>
        }
    }
  }

  <span class="hljs-keyword">if</span> (invokeCallback) {
    callback(
      traverseContext,
      children,
      nameSoFar === <span class="hljs-string">&apos;&apos;</span> ? SEPARATOR + getComponentKey(children, <span class="hljs-number">0</span>) : nameSoFar,
    )
    <span class="hljs-keyword">return</span> <span class="hljs-number">1</span>
  }

  <span class="hljs-keyword">let</span> child
  <span class="hljs-keyword">let</span> nextName
  <span class="hljs-keyword">let</span> subtreeCount = <span class="hljs-number">0</span> <span class="hljs-comment">// Count of children found in the current subtree.</span>
  <span class="hljs-keyword">const</span> nextNamePrefix = nameSoFar === <span class="hljs-string">&apos;&apos;</span> ? SEPARATOR : nameSoFar + SUBSEPARATOR

  <span class="hljs-keyword">if</span> (<span class="hljs-built_in">Array</span>.isArray(children)) {
    <span class="hljs-keyword">for</span> (<span class="hljs-keyword">let</span> i = <span class="hljs-number">0</span>; i &lt; children.length; i++) {
      child = children[i]
      nextName = nextNamePrefix + getComponentKey(child, i)
      subtreeCount += traverseAllChildrenImpl(
        child,
        nextName,
        callback,
        traverseContext,
      )
    }
  } <span class="hljs-keyword">else</span> {
    <span class="hljs-keyword">const</span> iteratorFn = getIteratorFn(children)
    <span class="hljs-keyword">if</span> (<span class="hljs-keyword">typeof</span> iteratorFn === <span class="hljs-string">&apos;function&apos;</span>) {
      <span class="hljs-comment">// iterator&#xFF0C;&#x548C;array&#x5DEE;&#x4E0D;&#x591A;</span>
    } <span class="hljs-keyword">else</span> <span class="hljs-keyword">if</span> (type === <span class="hljs-string">&apos;object&apos;</span>) {
      <span class="hljs-comment">// &#x63D0;&#x9192;&#x4E0D;&#x6B63;&#x786E;&#x7684;children&#x7C7B;&#x578B;</span>
    }
  }

  <span class="hljs-keyword">return</span> subtreeCount
}</code></pre>
<p>&#x8FD9;&#x91CC;&#x5C31;&#x662F;&#x4E00;&#x5C42;&#x9012;&#x5F52;&#x4E86;&#xFF0C;&#x5BF9;&#x4E8E;&#x53EF;&#x5FAA;&#x73AF;&#x7684;<code>children</code>&#xFF0C;&#x90FD;&#x4F1A;&#x91CD;&#x590D;&#x8C03;&#x7528;<code>traverseAllChildrenImpl</code>&#xFF0C;&#x76F4;&#x5230;&#x662F;&#x4E00;&#x4E2A;&#x8282;&#x70B9;&#x7684;&#x60C5;&#x51B5;&#xFF0C;&#x7136;&#x540E;&#x8C03;&#x7528;<code>callback</code>&#xFF0C;&#x4E5F;&#x5C31;&#x662F;<code>mapSingleChildIntoContext</code></p><pre><code class="lang-js"><span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">mapSingleChildIntoContext</span>(<span class="hljs-params">bookKeeping, child, childKey</span>) </span>{
  <span class="hljs-keyword">const</span> { result, keyPrefix, func, context } = bookKeeping

  <span class="hljs-keyword">let</span> mappedChild = func.call(context, child, bookKeeping.count++)
  <span class="hljs-keyword">if</span> (<span class="hljs-built_in">Array</span>.isArray(mappedChild)) {
    mapIntoWithKeyPrefixInternal(mappedChild, result, childKey, c =&gt; c)
  } <span class="hljs-keyword">else</span> <span class="hljs-keyword">if</span> (mappedChild != <span class="hljs-literal">null</span>) {
    <span class="hljs-keyword">if</span> (isValidElement(mappedChild)) {
      mappedChild = cloneAndReplaceKey(
        mappedChild,
        keyPrefix +
          (mappedChild.key &amp;&amp; (!child || child.key !== mappedChild.key)
            ? escapeUserProvidedKey(mappedChild.key) + <span class="hljs-string">&apos;/&apos;</span>
            : <span class="hljs-string">&apos;&apos;</span>) +
          childKey,
      )
    }
    result.push(mappedChild)
  }
}</code></pre>
<p><code>mapSingleChildIntoContext</code>&#x8FD9;&#x4E2A;&#x65B9;&#x6CD5;&#x5176;&#x5B9E;&#x5C31;&#x662F;&#x8C03;&#x7528;<code>React.Children.map(children, callback)</code>&#x8FD9;&#x91CC;&#x7684;<code>callback</code>&#xFF0C;&#x5C31;&#x662F;&#x6211;&#x4EEC;&#x4F20;&#x5165;&#x7684;&#x7B2C;&#x4E8C;&#x4E2A;&#x53C2;&#x6570;&#xFF0C;&#x5E76;&#x5F97;&#x5230;<code>map</code>&#x4E4B;&#x540E;&#x7684;&#x7ED3;&#x679C;&#x3002;&#x6CE8;&#x610F;&#x91CD;&#x70B9;&#x6765;&#x4E86;&#xFF0C;<strong>&#x5982;&#x679C;<code>map</code>&#x4E4B;&#x540E;&#x7684;&#x8282;&#x70B9;&#x8FD8;&#x662F;&#x4E00;&#x4E2A;&#x6570;&#x7EC4;&#xFF0C;&#x90A3;&#x4E48;&#x518D;&#x6B21;&#x8FDB;&#x5165;<code>mapIntoWithKeyPrefixInternal</code>&#xFF0C;&#x90A3;&#x4E48;&#x8FD9;&#x4E2A;&#x65F6;&#x5019;&#x6211;&#x4EEC;&#x5C31;&#x4F1A;&#x518D;&#x6B21;&#x4ECE;<code>pool</code>&#x91CC;&#x9762;&#x53BB;<code>context</code>&#x4E86;&#xFF0C;&#x800C;<code>pool</code>&#x7684;&#x610F;&#x4E49;&#x5927;&#x6982;&#x4E5F;&#x5C31;&#x662F;&#x5728;&#x8FD9;&#x91CC;&#x4E86;&#xFF0C;&#x5982;&#x679C;&#x5FAA;&#x73AF;&#x5D4C;&#x5957;&#x591A;&#x4E86;&#xFF0C;&#x53EF;&#x4EE5;&#x51CF;&#x5C11;&#x5F88;&#x591A;&#x5BF9;&#x8C61;&#x521B;&#x5EFA;&#x548C;<code>gc</code>&#x7684;&#x635F;&#x8017;&#x3002;</strong></p><p>&#x800C;&#x5982;&#x679C;&#x4E0D;&#x662F;&#x6570;&#x7EC4;&#x5E76;&#x4E14;&#x662F;&#x4E00;&#x4E2A;&#x5408;&#x89C4;&#x7684;<code>ReactElement</code>&#xFF0C;&#x5C31;&#x89E6;&#x8FBE;&#x9876;&#x70B9;&#x4E86;&#xFF0C;&#x66FF;&#x6362;&#x4E00;&#x4E0B;<code>key</code>&#x5C31;&#x63A8;&#x5165;<code>result</code>&#x4E86;&#x3002;</p><p>React &#x8FD9;&#x4E48;&#x5B9E;&#x73B0;&#x4E3B;&#x8981;&#x662F;&#x4E24;&#x4E2A;&#x76EE;&#x7684;&#xFF1A;</p><ol><li>&#x62C6;&#x5206;<code>map</code>&#x51FA;&#x6765;&#x7684;&#x6570;&#x7EC4;
</li>
<li>&#x56E0;&#x4E3A;&#x5BF9;<code>Children</code>&#x7684;&#x5904;&#x7406;&#x4E00;&#x822C;&#x5728;<code>render</code>&#x91CC;&#x9762;&#xFF0C;&#x6240;&#x4EE5;&#x4F1A;&#x6BD4;&#x8F83;&#x9891;&#x7E41;&#xFF0C;&#x6240;&#x4EE5;&#x8BBE;&#x7F6E;&#x4E00;&#x4E2A;<code>pool</code>&#x51CF;&#x5C11;&#x58F0;&#x660E;&#x548C;<code>gc</code>&#x7684;&#x5F00;&#x9500;
</li></ol>
<p>&#x8FD9;&#x5C31;&#x662F;<code>Children.map</code>&#x7684;&#x5B9E;&#x73B0;&#xFF0C;&#x867D;&#x7136;&#x4E0D;&#x7B97;&#x4EC0;&#x4E48;&#x7279;&#x522B;&#x795E;&#x5947;&#x7684;&#x4EE3;&#x7801;&#xFF0C;&#x4F46;&#x662F;&#x9605;&#x8BFB;&#x4E00;&#x4E0B;&#x8FD8;&#x662F;&#x633A;&#x6709;&#x610F;&#x601D;&#x7684;&#x3002;</p>
                                
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